.MSU File Extension
File TypeWindows Vista Update Package
This file is saved in a binary format, which requires a specific program to read its contents.
What is a MSU file?
Update file used by Windows Update, an application included with Windows Vista, Windows 7, and Windows Server; contains updates for applications and files; installed by the Windows Update Stand-alone Installer (Wusa.exe), which is run by Windows Update automatically (the user generally does not need to manually install MSU files).
Each MSU file contains four elements:
- Windows Update metadata, which describes the update package
- One or more .CAB files that store the update data for the package
- An .XML file which describes the contents of the MSU file
- A properties file that is read by Wusa.exe
You can manually extract the contents of an MSU file at the Windows command prompt by typing:
expand -f:* "example.msu" output_directory
You can then manually install the update package by typing the following command:
(example.msu and example.xml have the same filename prefix).
NOTE: Earlier versions of the Windows operating system used .MSI files for updates.